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Last Post 25 Dec 2009 12:10 PM by  glenn@traileroutlet.com
No inside lights on enclosed trailer - 2004 Yukon XL2500
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VetteExplorer
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24 Sep 2008 12:56 AM

    Any/all help greatly appreciated.

    Just changed tow vehicles from a 2001 Yukon to a 2004 Yukon XL2500. My interior trailer lights worked fine before. Now, no lights.

    I checked out the connector on the Yukon, and the pin that looks to be 12 volts hot,,,,,,,isn't. I've checked all the fuses. All check OK?

    Any ideas?

    TIA

    Impala SS AutoXer
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    24 Sep 2008 01:40 AM

    At least in the 2500HD trucks, there is an underhood "square" fuse that you have to put in for that constant +12V to work. The fuse is NOT installed from the factory, but is usually taped up with the OEM trailer brake controller harness pigtail (usually comes in the glovebox new).

    So check the underhood fusebox, if a fuse is missing that is probably it...

    tholt29
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    24 Sep 2008 10:31 AM

    Also, on my 02 F250, that circuit is only hot when the key is in the auxiliary or on position... We put a jumper in place of that relay. Check it with the truck on...

    Tom

    Impala SS AutoXer
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    24 Sep 2008 02:13 PM
    tholt29 wrote:

    Also, on my 02 F250, that circuit is only hot when the key is in the auxiliary or on position... We put a jumper in place of that relay. Check it with the truck on...

    Tom

    FYI, Ford makes it key-switched, GM makes it +12V all the time.

    hzl6cm
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    24 Sep 2008 03:35 PM
    Impala SS AutoXer wrote:

    At least in the 2500HD trucks, there is an underhood "square" fuse that you have to put in for that constant +12V to work. The fuse is NOT installed from the factory, but is usually taped up with the OEM trailer brake controller harness pigtail (usually comes in the glovebox new).

    So check the underhood fusebox, if a fuse is missing that is probably it...

    I agree, when we switched from our 2001 1/2 ton Suburban to our 2005 3/4 ton Suburban, there was no change in how +12v line in the trailering wiring. You do have to install the fuse mentioned above to make the wire hot, but we had to do that in '01 also.

    If I recall correctly though there is a difference in the brake controller harness pigtail so you can't use one from your earlier vehicle in the '04 without switching a couple of the wires around (let me know if you need those instructions, I think I still have them around somewhere), or use the one that came with the '04. In my case I was reusing the brake controller so it was easier to switch the two wires around in the '01 pigtail than it was to rewire the controller to the '05 pigtail.

    VetteExplorer
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    25 Sep 2008 11:31 PM

    Thanks everyone.

    The Yukon didn't come with the harness/fuse. I hooked up my brake controller harness from the old Yukon, and it works perfectly.

    I checked all the fuses under the hood, but didn't "add" a fuse. BINGO........I hope!

    Is this "square" fuse a relay?

    Thanks again.


    VetteExplorer
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    28 Sep 2008 01:38 AM

    [quote]

    If I recall correctly though there is a difference in the brake controller harness pigtail so you can't use one from your earlier vehicle in the '04 without switching a couple of the wires around (let me know if you need those instructions, I think I still have them around somewhere), or use the one that came with the '04. In my case I was reusing the brake controller so it was easier to switch the two wires around in the '01 pigtail than it was to rewire the controller to the '05 pigtail.

    Well, I think I located where the fuse goes. It has a plastic plug that says B+ there now. I need to put a meter to it and check it out. Do you remember what the current rating on the fuse is? There is mention of the fuse and harness in the owners manual, but absolutely no details!

    Now I'm a little concerned on the harness and controller. When I changed vehicles, I also changed controllers. I took the old harness and wired the new controller like the old one. It has worked for a for 2 trips, but I did have one time on the last trip when it kind of flaked out for a while. By chance do you have the color break outs still?

    Thanks again!

    lowflyer
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    09 Sep 2009 10:53 PM

    Don't know if this will help, but I recently bought a 2008 Trailblazer to haul my car in a Haulmak trailer.

    The interior lights on the trailer didn't work before or after hooking up a brake controller (which worked fine)

    I found that there is a separate wire, next to the main fuse box under the hood which needs to go to a "hot" post on the fuse panel. This not only allows for interior lights, but also recharges the break-away brake battery on the tongue of the trailer.

    GM seems to enjoy changing the set-up for trailer brakes every couple of years. The Trailblazers used to have (as most GM trucks did) a simple plug in on the inside of the firewall, just above the parking brake pedal. They did away with it on most of the "light trucks" to save a few $$ per vehicle.

    Hope this helps.

    JDerstine
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    24 Oct 2009 01:14 PM
    VetteExplorer wrote:

    [quote]

    If I recall correctly though there is a difference in the brake controller harness pigtail so you can't use one from your earlier vehicle in the '04 without switching a couple of the wires around (let me know if you need those instructions, I think I still have them around somewhere), or use the one that came with the '04. In my case I was reusing the brake controller so it was easier to switch the two wires around in the '01 pigtail than it was to rewire the controller to the '05 pigtail.

    Well, I think I located where the fuse goes. It has a plastic plug that says B+ there now. I need to put a meter to it and check it out. Do you remember what the current rating on the fuse is? There is mention of the fuse and harness in the owners manual, but absolutely no details!

    Now I'm a little concerned on the harness and controller. When I changed vehicles, I also changed controllers. I took the old harness and wired the new controller like the old one. It has worked for a for 2 trips, but I did have one time on the last trip when it kind of flaked out for a while. By chance do you have the color break outs still?

    Thanks again!

    It's a big 40 amp fuse. It goes in the second position back from the front ( at least with my '01 2500 Suburban )

    Here's a link to the trailer wiring diagram I found and posted here. http://sccaforums.com/forums/thread/375481.aspx

    Jeff

    glenn@traileroutlet.com
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    25 Dec 2009 12:10 PM
    Chevy / GM trucks have a " Power Distribution " / fuse box under the hood - driver side over the fender area. Many times , there is either no fuse, or a fake ( dummy fuse ) in either the brake controller, or charge wire circuits. Fuses need to be installed. Refer to your owners manual for location, and amperage . Additionally, a lot of the time they do not hook the wires up to the feed studs in that box. The brake controller feed wire is - depending on year of vehicle , either blue , or red - usually about 14 gauge wire, and is either loose inside ( you need to remove the entire lower cover ) or tucked in with the wire harness behind - toward the firewall . The charge wire is usually red - 12 gauge , and is usually tucked in - taped to the wire harness traveling down toward the steering column. Both wires usually have an end loop on them, and need to be attached to the 2 studs at the front ( away from the firewall ) end of the power distribution box. These require metric nuts that are not provided. Check your vehicles fuse finder page to look for Trailer + , and trailer brake fuses. Also note, there are usually 3 separate small fuses in that power distribution box for Trailer marker / tailights, and separate fuses for left, and right blinker / brake light circuits. Glenn


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